The present invention relates to thermoplastic polymer compositions, particularly to thermoplastic compositions containing isotactic polypropylene and a flexible propylene polymer having reduced isotacticity and to a process for the preparation thereof. The invention relates also to manufactured articles obtainable from those compositions.
Isotactic polypropylene is usually obtained by using Ziegler-Natta catalysts, that produce highly isotactic polymers with a broad distribution of molecular weight. More recently metallocene-based catalysts have been used in the polymerization reaction of olefins. Operating in the presence of these catalysts, polymers characterised by a narrow molecular weight distribution and having structural characteristics of interest have been obtained. By polymerizing propylene in the presence of metallocene catalysts, amorphous or highly crystalline polypropylenes can be obtained depending on the metallocene used, such as for example as described in EP 604 908 and EP 485 820. Amorphous polypropylene shows a poor stiffness, while the highly stereoregular and crystalline polypropylene thus obtained is characterised by good stiffness, but is unsatisfactory when high flexibility is required.
Several attempts have been made to improve the elastic properties of isotactic polypropylene by blending it with a xe2x80x9csofterxe2x80x9d polymer. For example in U.S. Pat. No. 4,521,566 polypropylene compositions are prepared in a multistage process which comprises at least one stage of propylene homopolymerization and at least one stage of ethylene/propylene copolymerization in the presence, in both stages, of a catalyst comprising a compound of titanium supported on a magnesium halide in active form. U.S. Pat. No. 5,539,056 describes a blend of high molecular weight amorphous polypropylene with low molecular weight isotactic polypropylene.
In U.S. Pat. No. 5,589,549 and U.S. Pat. No. 5,648,422 there are described multistep processes wherein in a first step a porous isotactic polypropylene is prepared in the presence of a titanium-based catalyst. In a second step, in the presence of the said porous polymer and a metallocene-based catalyst one or more olefins are polymerized.
Compositions of propylene polymers have now been found which show an improved balance of flexible-mechanical properties. Thus, according to a first aspect of the present invention, it is provided a thermoplastic composition comprising:
(A) 10 to 99% by weight of a propylene polymer optionally containing from 0.1 to 5% by moles of units deriving from an olefin of formula CH2xe2x95x90CHR, R being hydrogen, a C2-C20-alkyl or a C6-C12-aryl group, having the following characteristics:
50 less than isotactic triads (mm) less than 85;
melting point (Tm) from 60xc2x0 C. to 120xc2x0 C.; and
(B) 1 to 90% by weight of a propylene polymer optionally containing from 0.1 to 5% by moles of units deriving from an olefin of formula CH2xe2x95x90CHR, R being hydrogen, a C2-C20-alkyl or a C6-C12-aryl group, having the following characteristic:
an essentially isotactic structure;
melting point (Tm) higher than 153xc2x0 C.
The ratio of the quantities by weight of the components (A)/(B) of the composition according to the present invention is preferably comprised from 30:70 to 95:5, still more preferably from 40:60 to 90:10.
Preferably the polymer used as component (A) has a melting enthalpy less than 70 J/g.
Preferably, the melting point (Tm) of the propylene polymer used as component (B) is higher than 155xc2x0 C., most preferably higher than 160xc2x0 C.
It has been observed that the compositions according to the present invention have very good flexible-mechanical properties, even under high deformation, which are remarkably improved as compared to those of the single component. These elastic properties are reflected in improved impact strength. Thus, the compositions of the present invention are particularly useful for the manufacture of articles for which a high mechanical strength is required.
Propylene polymers that can be used as component (A) in the composition of the present invention as well as a process for the preparation thereof are described, for example, by U. Dietrich et al, in J. Am. Chem. Soc. 1999, 121, 4348-4355, the contents of which are to be incorporated by reference in the present description.
A particular useful method for obtaining the propylene polymer of component (A) of the composition of the present invention is described in the copending Application PCT/EP00/3191 in the name of the same Applicant.
The propylene polymers of component (A) have low crystallinity. Their melting enthalpy values (xcex94Hf) are preferably lower than  less than 70 J/g. Their intrinsic viscosity values [xcex7] are preferably higher than 0.5, more preferably higher than 0.8.
Preferably the propylene polymer of component (A) has a melting point (Tm) of from 80xc2x0 C. to 120xc2x0 C.
13C-NMR analysis carried out on the above propylene polymer as used in component (A) of the composition of the present invention provides information on the tacticity of the polymer chains. It is observed that the percentage of isotactic triads (mm) is from 50 to 85. Preferably in the propylene polymer the isotactic triads (mm) satisfy the relation 60 less than isotactic triads (mm) less than 80.
The molecular weights of the above propylene polymers are distributed within fairly narrow ranges. Thus the molecular weight distribution Mw/Mn turns out to be generally lower than 5, preferably lower than 4, more preferably lower than 3.
Examples of isotactic polymers of propylene for use as component (B) are commercially available isotactic polypropylenes, which are produced by means of conventional titanium based heterogeneous Ziegler-Natta-type catalysts. Metallocene based isotactic polymers having the above-described characteristics can also be used. Suitable metallocenes of this type are described in WO 96/22995. Polymers made by means of metallocenes generally have narrow molecular weight distribution Mw/Mn, such as values of lower than 3.
Generally the essentially isotactic propylene polymer used as component (B) of the compositions of the present invention have the following characteristics:
melting enthalpy greater than 70 J/g, and
% of isotactic triads mm (B) greater than % of isotactic triads mm (A).
The structure of the above propylene polymer used as component (B) in the thermoplastic composition according to the present invention is essentially isotactic. In fact the percentage of isotactic triads (mm) is preferably higher than 90, more preferably the percentage of isotactic triads (mm) is higher than 95.
The essentially isotactic propylene polymer used in component (13) of the composition of the present invention have intrinsic viscosity values [xcex7] of preferably higher than 1 dl/g. The propylene polymer as used as components (A) and (B) in the composition of the present invention can contain co-monomer units, such as ethylene, 1-butene, styrene, 1,5-hexadiene, 4-methylpentene or allyltrimethylsilane.
In the thermoplastic composition according to the present invention, the melting enthalpy xcex94H in the melting range of from about 39xc2x0 C. to about 130xc2x0 C. is generally higher than 6 J/g, preferably higher than 20 J/g. The thermoplastic composition according to the present invention can contain additives which are conventionally employed in thermoplastic polymer compositions such as stabilisers, antioxidants, corrosion inhibitors and the like.
Moreover, the compositions of the present invention can contain inorganic, organic or polymeric fillers. The above additives and fillers can be used in conventional quantities, as is known to those skilled in the art. Generally said additives and fillers can be present in a quantity of 5% by weight of the overall composition. Another aspect of the present invention is a process for the preparation of a thermoplastic composition as defined above, comprising the steps:
(I) polymerizing propylene optionally with an olefin of the formula CH2xe2x95x90CHR, R being hydrogen, a C1-C20-alkyl or a C6-C12-aryl group, in one or more reactors, in the presence of a catalyst comprising the product between an Al-alkyl compound and a solid component comprising at least one non-metallocene compound of a transition metal M1 containing Ti and not containing M1-xcfx80 bonds and a magnesium halide;
(II) optionally deactivating the catalyst used under (I) and contacting the product as obtained under step (I) with
(A) a metallocene compound of the general formula (I):
L1Z1G1M2X1pxe2x80x83xe2x80x83(I) 
wherein L1 is a divalent bridging group;
Z1 is a moiety of formula (II): 
wherein R2 and R3, same or different from each other, are selected from hydrogen, a C1-C20-alkyl, C3-C20-cycloalkyl, C2-C20-alkenyl, C6-C20-aryl, C7-C20-alkylaryl, C7-C20-arylalkyl radical, optionally containing heteroatoms belonging to groups 13-17 of the Periodic Table of the Elements, preferably at least one of R2 and R3 being different from hydrogen;
A and B are selected from S, O or CR4, wherein R4 is selected from hydrogen, a C1-C20-alkyl, C3-C20-cycloalkyl, C2-C20-alkenyl, C6-C20a-aryl, C7-C20-alkylaryl, C7-C20-arylalkyl radical, optionally containing heteroatoms belonging to groups 13-17 of the Periodic Table of the Elements, either A or B being different from CR5, and wherein the rings containing A and B have a double bond in any of the allowed positions;
G1 is a moiety of formula (III): 
wherein R5, R6, and R8, same or different from each other, are selected from hydrogen, a C1-C20-alkyl, C3-C20-cycloalkyl, C2-C20-alkenyl, C6-C20-aryl, C7-C20-alkylaryl, C7-C20-arylalkyl radical, optionally containing heteroatoms belonging to groups 13-17 of the Periodic Table of the Elements, and R5 and le can form a ring comprising from 3 to 8 atoms, which can bear substituents;
M2 is an atom of a transition metal selected from those belonging to group 3, 4, 5, and 6 or to the lanthanide or actinide groups in the Periodic Table of the Elements (IUPAC),
X1, same or different, is selected from hydrogen, a halogen atom, a R9, OR9, OSO2CF3, OCOR9, SR9, NR92 or PR92 group, wherein the substituents R9 are selected from hydrogen, a C1-C20-alkyl, C3-C20-cycloalkyl, C2-C20-alkenyl, C6-C20-aryl, C7-C20-alkylaryl, C7-C20-arylalkyl radical, optionally containing heteroatoms;
p is an integer of from 0 to 3, being equal to the Oxidation State of the metal M minus 2; and/or with
(Axe2x80x2) a metallocene compound of the general formula (IV):
L2G2Z2M3X2qxe2x80x83xe2x80x83(IV) 
wherein;
G2 is a moiety of formula (V); 
wherein
the ring substituted with R11 and R10 groups have double bonds in any of the allowed positions;
R10 and R11, same or different from each other, are selected from hydrogen, a C1-C20-alkyl, C3-C20-cycloalkyl, C2-C20-alkenyl, C6-C2-aryl, C7-C20-alkylaryl, C7-C20-arylalkyl radical, optionally containing heteroatoms, wherein two R10 and/or R11 can form a ring comprising 4 to 8 atoms, which can bear substituents;
e and f, same or different from each other, are integers comprised from 1 to 6; preferably comprised from 2 to 5 more preferably from 3 to 4; and
Z2 is a moiety of formula (VI): 
wherein
A, B and D, same or different from each other, are selected from an element of the groups 13 to 16 of the Periodic Table of the Elements (IUPAC);
R12, R13, R14, R15 and R16, same or different from each other, are selected from hydrogen, a C1-C20-alkyl, C3-C20-cycloalkyl, C2-C20-alkenyl, C6-C20-aryl, C7-C20-alkylaryl, C7-C20-arylalkyl radical, optionally containing heteroatoms; wherein two R14 can form a ring comprising 4 to 8 atoms, and any of two adjacent R14, R15 and R16 can form a ring comprising 4 to 8 atoms, which can bear substituents;
n, m and s are selected from 0, 1 and 2;
n, m and s being 0 when A, B and D are selected from an element of the group 16 of the Periodic Table of the Elements (IUPAC);
n, m and s being 1 when A, B and D are selected from an element of the groups 13 and 15 of the Periodic Table of the Elements (IUPAC);
n, m and s being 1 or 2 when A, B and D are selected from an element of the group 14 of the Periodic Table of the Elements (IUPAC);
and wherein the ring containing A, B and D can have double bonds in any of the allowed positions;
or Z2 is a moiety of formula (VII): 
wherein
R17, R18, R19, R20, R21 and R22, same or different from each other, are selected from hydrogen, a C1-C20-alkyl, C3-C20-cycloalkyl, C2-C20-alkenyl, C6-C20-aryl, C7C20alkylaryl, C7-C20-arylalkyl radical, optionally containing heteroatoms, optionally any of two adjacent R19, R20, R21 and R22 can form a ring comprising 4 to 8 atoms which can bear substituents.
L2 is a divalent bridging group;
M3 is an atom of a transition metal selected from those belonging to group 3, 4, 5, and 6 or to the lanthanide or actinide groups in the Periodic Table of the Elements (IUPAC),
X2, same or different, is a hydrogen atom, a halogen atom, a R23, OR23, OSO2CF3, OCOR23, SR23, NR232 or PR232 group, wherein the substituents R23 are selected from hydrogen, a C1-C20-alkyl, C3-C20-cycloalkyl, C2-C20-alkenyl, C6-C20-aryl, C7-C20-alkylaryl, C7-C20-arylalkyl radical, optionally containing heteroatoms;
q is an integer of from 0 to 3, being equal to the Oxidation State of the metal M minus 2; and
(B) optionally a suitable cocatalyst and/or an Al-alkyl compound;
(III) polymerizing propylene optionally with one or more of an olefin of formula CH2xe2x95x90CHR, R being hydrogen, a C1-C20-alkyl or a C6-C12-aryl group, in one or more reactors, in the presence of the product obtained in step (II).
The transition metals M2 and M3 are preferably selected from titanium, zirconium and hafnium. The X1 and X2 substituents are preferably chlorine atoms or methyl groups. Preferably the bridging groups L1 and L2 are a  greater than CMe2 or  greater than SiMe2 group.
When a metallocene compound of formula (I) containing a moiety of formula (III) is used, preferably R5 and R8, same or different from each other, are selected from hydrogen, a C1-C20-alkyl, C3-C20-cycloalkyl, C2-C20-alkenyl, C6-C20-aryl, C7-C20-alkylaryl, C7-C20-arylalkyl radical, optionally containing heteroatoms belonging to groups 13-17 of the Periodic Table of the Elements; R6 is selected from a C7-C20-alkylaryl or a QR24R25R26 group, wherein Q is selected from C, Si, Ge; R14, R25 and R26, same or different from each other, are hydrogen, C1-C20-alkyl, C3-C20-cycloalkyl, C2-C20-alkenyl, C6-C20-aryl, C7-C20-alkylaryl, C7-C20-arylalkyl radicals, optionally containing heteroatoms belonging to groups 13-17 of the Periodic Table of the Elements, with the proviso that when Q is a carbon atom, at least one of R26, R27 and R28 is a hydrogen atom.
Particularly preferred metallocenes of the above mentioned class are those wherein R6 is selected from a CHR24R25 group and a SiR24R25R26 group, R24, R25 and R26 being hydrogen or C1-C20-alkyl groups.
Most preferred are those metallocene wherein QR24R25R26 is an isopropyl or a trimethylsilyl group.
Another preferred structure of the moiety of formula (III) is a moiety of formula (IIIa) 
wherein R33, R34 R35, R36 and R37 same or different from each other, are selected from hydrogen, a C1-C20-alkyl, C3-C20-cycloalkyl, C2-C20-alkenyl, C6-C20-aryl, C7-C20alkylaryl, C7-C20-arylalkyl radical, optionally containing heteroatoms, optionally any of two adjacent R34, R35, R36 and R37 can form a ring comprising 4 to 8 atoms which can bear substituents;
preferably R33 is C1-C20-alkyl, more preferably is methyl; R37 is preferably C1-C20-alkyl, C6-C20-aryl or can form with R36 a condensed benzene ring.
Preferably in the metallocene compound of formula (I) one of A and B is a sulphur atom and the other is a CH group; more preferably A is sulphur. Preferably R2 and R3 are the same and are selected from a C1-C20-alkyl group, which can contain a silicon atom. Most preferably R2 and R3 are a methyl or a trimethylsilyl radical.
Non-limiting examples of metallocene compounds of formula (I) useful in the process of the present invention are:
methylene(3-methyl-cyclopentadienyl)-7-(2,5-dimethylcyclopentadienyl-[1,2-b:4,3-bxe2x80x2]dithiophene)zirconium dichloride and dimethyl;
methylene(3-ethyl-cyclopentadienyl)-7-(2,5-dimethylcyclopentadienyl-[1,2-b:4,3-bxe2x80x2]dithiophene)zirconium dichloride and dimethyl;
methylene(3-isopropyl-cyclopentadienyl)-7-(2,5-dimethylcyclopentadienyl-[1,2-b:4,3-bxe2x80x2]dithiophene)zirconium dichloride and dimethyl;
methylene(2,4-dimethyl-cyclopentadienyl)-7-(2,5-dimethylcyclopentadienyl-[1,2-b:4,3-bxe2x80x2]dithiophene)zirconium dichloride and dimethyl;
methylene(2,4-diethyl-cyclopentadienyl)-7-(2,5-dimethylcyclopentadienyl-[1,2-b:4,3-bxe2x80x2]dithiophene)zirconium dichloride and dimethyl;
methylene(2,4-diisopropyl-cyclopentadienyl)-7-(2,5-dimethylcyclopentadienyl-[1,2-b:4,3-bxe2x80x2]dithiophene)zirconium dichloride and dimethyl;
methylene(2,3,5-trimethyl-cyclopentadienyl)-7-(2,5-dimethylcyclopentadienyl-[1,2-b:4,3-bxe2x80x2]dithiophene)zirconium dichloride and dimethyl;
methylene(2,3,5-triethyl-cyclopentadienyl)-7-(2,5-dimethylcyclopentadienyl-[1,2-b:4,3-bxe2x80x2]dithiophene)zirconium dichloride and dimethyl;
methylene(2,3,5-triisopropyl-cyclopentadienyl)-7-(2,5-dimethylcyclopentadienyl-[1,2-b:4,3-bxe2x80x2]dithiophene)zirconium dichloride and dimethyl;
methylene(3-cyclohexyl-cyclopentadienyl)-7-(2,5-dimethylcyclopentadienyl-[1,2-b:4,3-bxe2x80x2]dithiophene)zirconium dichloride and dimethyl;
methylene-1-(tetrahydroindenyl)7-(2,5-dimethylcyclopentadienyl-[1,2-b:4,3-bxe2x80x2]dithiophene)zirconium dichloride and dimethyl;
isopropylidene(3-methyl-cyclopentadienyl)-7-(2,5-dimethylcyclopentadienyl-[1,2-b:4,3-bxe2x80x2]dithiophene)zirconium dichloride and dimethyl;
isopropylidene(3-ethyl-cyclopentadienyl)-7-(2,5-dimethylcyclopentadienyl-[1,2-b:4,3-bxe2x80x2]dithiophene)zirconium dichloride and dimethyl;
isopropylidene(3-isopropyl-cyclopentadienyl)-7-(2,5-dimethylcyclopentadienyl-[1,2-b:4,3-bxe2x80x2]dithiophene)zirconium dichloride and dimethyl;
isopropylidene(3-phenyl-cyclopentadienyl)-7-(2,5-dimethylcyclopentadienyl-[1,2-b:4,3-bxe2x80x2]dithiophene)zirconium dichloride and dimethyl;
isopropylidene(2,4-dimethyl-cyclopentadienyl)-7-(2,5-dimethylcyclopentadienyl-[1,2-b:4,3-bxe2x80x2]dithiophene)zirconium dichloride and dimethyl;
isopropylidene(2,4-dimethyl-cyclopentadienyl)-7-(2,5-ditrimethylsilylcyclopentadienyl-[1,2-b:4,3-bxe2x80x2]dithiophene)zirconium dichloride and dimethyl;
isopropylidene(2,4-diethyl-cyclopentadienyl)-7-(2,5-dimethylcyclopentadienyl-[1,2-b:4,3-bxe2x80x2]dithiophene)zirconium dichloride and dimethyl;
isopropylidene(2,4-diisopropyl-cyclopentadienyl)-7-(2,5-dimethylcyclopentadienyl-[1,2-b:4,3-bxe2x80x2]dithiophene)zirconium dichloride and dimethyl;
isopropylidene(2-methyl-4-phenyl-cyclopentadienyl)-7-(2,5-dimethylcyclopentadienyl-[1,2-b:4,3-bxe2x80x2]dithiophene)zirconium dichloride and dimethyl;
isopropylidene(2-methyl-4-phenyl-cyclopentadienyl)-7-(2,5-ditrimethylsilylcyclopentadienyl-[1,2-b:4.3-bxe2x80x2]dithiophene)zirconium dichloride and dimethyl;
isopropylidene(2-methyl-4-isopropyl-cyclopentadienyl)-7-(2,5-dimethylcyclopentadienyl-[1,2-b:4,3-bxe2x80x2]dithiophene)zirconium dichloride and dimethyl;
isopropylidene(2,3,5-trimethyl-cyclopentadienyl)-7-(2,5-dimethylcyclopentadienyl-[1,2-b:4,3-bxe2x80x2]dithiophene)zirconium dichloride and dimethyl;
isopropylidene(2,3,5-triethyl-cyclopentadienyl)-7-(2,5-dimethylcyclopentadienyl-[1,2-b:4,3-bxe2x80x2]dithiophene)zirconium dichloride and dimethyl;
isopropylidene(2,3,5-triisopropyl-cyclopentadienyl)-7-(2,5-dimethylcyclopentadienyl-[1,2-b:4,3-bxe2x80x2]dithiophene)zirconium dichloride and dimethyl;
isopropylidene(3-cyclohexyl-cyclopentadienyl)-7-(2,5-dimethylcyclopentadienyl-[1,2-b:4,3-bxe2x80x2]dithiophene)zirconium dichloride and dimethyl;
isopropylidene(3-isopropyl-cyclopentadienyl)-7-(2,5-ditrimethylsilylcyclopentadienyl-[1,2-b:4,3-bxe2x80x2]dithiophene)zirconium dichloride and dimethyl;
isopropylidene(3-isopropyl-cyclopentadienyl)-4-(2,6-dimethylcyclopentadienyl-[2,1-b:3,4-bxe2x80x2]dithiophene)zirconium dichloride and dimethyl;
isopropylidene-1-(tetrahydroindenyl)-7-(2,5-dimethylcyclopentadienyl-[1,2-b:4,3-bxe2x80x2]dithiophene)zirconium dichloride and dimethyl;
isopropylidene(3-methyl-cyclopentadienyl)-4-(2,6-dimethylcyclopentadienyl-[2,1-b:3,4-bxe2x80x2]dithiophene)hafnium dichloride and dimethyl;
dimethylsilandiyl(3-methyl-cyclopentadienyl)-7-(2,5-dimethylcyclopentadienyl-[1,2-b:4,3-bxe2x80x2]dithiophene)zirconium dichloride and dimethyl;
dimethylsilandiyl(3-ethyl-cyclopentadienyl)-7-(2.5-dimethylcyclopentadienyl-[1,2-b:4,3-bxe2x80x2]dithiophene)zirconium dichloride and dimethyl;
dimethylsilandiyl(3-isopropyl-cyclopentadienyl)7-(2,5-dimethylcyclopentadienyl-[1,2-b:4,3-bxe2x80x2]dithiophene)zirconium dichloride and dimethyl;
dimethylsilandiyl(3-phenyl-cyclopentadienyl)-7-(2,5-dimethylcyclopentadienyl-[1,2-b:4,3-bxe2x80x2]dithiophene)zirconium dichloride and dimethyl;
dimethylsilandiyl(2,4-dimethyl-cyclopentadienyl)-7-(2,5-dimethylcyclopentadienyl-[1,2-b:4,3-bxe2x80x2) dithiophene)zirconium dichloride and dimethyl;
dimethylsilandiyl(2,4-diethyl-cyclopentadienyl)-7-(2,5-dimethylcyclopentadienyl-[1,2-b:4,3-bxe2x80x2]dithiophene)zirconium dichloride and dimethyl;
dimethylsilandiyl(2,4-diisopropyl-cyclopentadienyl)-7-(2,5-dimethylcyclopentadienyl-[1,2-b:4,3-bxe2x80x2]dithiophene)zirconium dichloride and dimethyl;
dimethylsilandiyl(2,3,5-trimethyl-cyclopentadienyl)-7-(2,5-dimethylcyclopentadienyl-[1,2-b:4,3-bxe2x80x2]dithiophene)zirconium dichloride and dimethyl;
dimethylsilandiyl(2,3,5-triethyl-cyclopentadienyl)-7-(2,5-dimethylcyclopentadienyl-[1,2-b:4,3-bxe2x80x2]dithiophene)zirconium dichloride and dimethyl;
dimethylsilandiyl(2,3,5-triisopropyl-cyclopentadienyl)-7-(2,5-dimethylcyclopentadienyl-[1,2-b:4,3-bxe2x80x2]dithiophene)zirconium dichloride and dimethyl;
dimethylsilandiyl(3-cyclohexyl-cyclopentadienyl)-7-(2,5-dimethylcyclopentadienyl-[1,2-b:4,3-bxe2x80x2]dithiophene)zirconium dichloride and dimethyl;
dimethylsilandiyl(3-trimethylsilyl-cyclopentadienyl)-7-(2,5-dimethylcyclopentadienyl-[1,2-b:4,3-bxe2x80x2]dithiophene)zirconium dichloride and dimethyl;
dimethylsilandiyl-1-(indenyl)-7-(2,5-dimethylcyclopentadienyl-[1,2-b:4,3-bxe2x80x2]dithiophene)zirconium dichloride and dimethyl;
dimethylsilandiyl-1-(2-methyl-indenyl)-7-(2,5-dimethylcyclopentadienyl-[1,2-b:4,3-bxe2x80x2]dithiophene)zirconium dichloride and dimethyl;
dimethylsilandiyl-1-(2-ethyl-indenyl)-7-(2,5-dimethylcyclopentadienyl-[1,2-b:4,3-bxe2x80x2]dithiophene)zirconium dichloride and dimethyl;
dimethylsilandiyl-1-(2-isopropyl-indenyl)-7-(2,5-dimethylcyclopentadienyl-[1,2-b:4,3-bxe2x80x2]dithiophene)zirconium dichloride and dimethyl;
dimethylsilandiyl-1-(2-isopropyl-indenyl)-4(2,6-dimethylcyclopentadienyl-[2,1-b:3,4-bxe2x80x2]dithiophene)zirconium dichloride and dimethyl;
dimethylsilandiyl-1-(2-isopropyl-indenyl)7-(2,5-ditrimethylsilylcyclopentadienyl-[1,2-b:4,3-bxe2x80x2]dithiophene)zirconium dichloride and dimethyl;
dimethylsilandiyl-1-(2-methyl-indenyl)-7-(2,5-dimethylcyclopentadienyl-[1,2-b:4,3-bxe2x80x2]dithiophene)hafnium dichloride and dimethyl;
dimethylsilandiyl-1-(tetrahydroindenyl)-7-(2,5-dimethylcyclopentadienyl-[1,2-b:4,3-bxe2x80x2]dithiophene)zirconium dichloride and dimethyl;
isopropylidene(3-isopropyl-cyclopentadienyl)-7-(2,5-dimethyl-cyclopentadienyl-[1,2-b:4,3-bxe2x80x2]dithiophene)zirconium dichloride;
isopropylidene(3-methyl-cyclopentadienyl)-7-(2,5-dimethyl-cyclopentadienyl-[1,2-b:4,3-bxe2x80x2]-dithiophene)zirconium dichloride;
isopropylidene(3-isopropyl-cyclopentadienyl)-7-(2,5-ditrimethylsilyl-cyclopentadienyl-[1,2-b:4,3-bxe2x80x2]-dithiophene)zirconium dichloride;
isopropylidene(3-isopropyl-cyclopentadienyl)-4-(2,6-dimethyl-cyclopentadienyl-[2,1-b:3,4-bxe2x80x2]-dithiophene)zirconium dichloride;
dimethylsilandiyl-1-(indenyl)-7-(2,5-dimethyl-cyclopentadienyl-[1,2-b:4,3-bxe2x80x2]-dithiophene)zirconium dichloride;
isopropylidene(2-methyl-4-phenyl-cyclopentadienyl)-7-(2,5-dimethyl-cyclopentadienyl-[1,2-b:4,3-bxe2x80x2]-dithiophene)zirconium dichloride;
isopropylidene(2,4-dimethyl-cyclopentadienyl)-7-(2,5-dimethyl-cyclopentadienyl-[1,2-b:4,3-bxe2x80x2]-dithiophene)zirconium dichloride;
isopropylidene(3-methyl-cyclopentadienyl)-7-(2,5-dimethyl-cyclopentadienyl-[1,2-b:4,3-bxe2x80x2]-dithiophene)hafnium dichloride;
isopropylidene(3-isopropyl-cyclopentadienyl)-7-(2,5-ditrimethylsilyl-cyclopentadienyl-[1,2-b:4,3-bxe2x80x2]-dithiophene)zirconium dichloride;
isopropylidene(3-isopropyl-cyclopentadienyl)-4-(2,6-dimethyl-cyclopentadienyl-[2,1-b:3,4-bxe2x80x2]-dithiophene)zirconium dichloride.
Preferably dimethylsilandiyl-1-(2-methyl-indenyl)-7-(2,5-dimethylcyclopentadienyl-[1,2-b:4,3-bxe2x80x2]dithiophene)zirconium dichloride and dimethylsilandiyl-1-(indenyl)-7-(2,5-dimethylcyclopentadienyl-[1,2-b:4,3-bxe2x80x2]dithiophene)zirconium dichloride, dimethylsilandiyl-1-(2-methyl-benz[e]indenyl)-7-(2,5-dimethylcyclopentadienyl-[1,2-b:4,3-bxe2x80x2]dithiophene)zirconium are used.
When a metallocene of the formula (IV) is used in the process of the present invention G2 is preferably a fluorenyl or substituted fluorenyl radical.
Preferably in the moiety of formula (VI) R12 is a C1-C20-alkyl radical, R14 is a C6-C20-aryl radical, R13, R15 and R16 are hydrogen, A and B are carbon atoms and D is nitrogen.
Preferably in the moiety of formula (VII) R19 and R20 form a ring comprising 6 carbon atoms, for example a benz[e]indenyl or a cyclohexaindenyl moiety, or R20 and R22 form a ring comprising 5 carbon atoms.
Non-limiting examples of metallocenes of formula (IV) useful in the process of the present invention are:
[1-(9-xcex75-fluorenyl)-2-(2-methylbenz[e]-1-xcex75-indenyl)ethane]-zirconium dichloride and dimethyl;
[1-(9-xcex75-fluorenyl)-2-(4,5-cyclohexa-2-methyl-1-xcex75-indenyl)ethane]-zirconium dichloride and dimethyl;
[1-(9-xcex75-fluorenyl)-2-(5,6-cyclopenta-2-methyl-1-indenyl)ethane]-zirconium dichloride and dimethyl.
Metallocenes of the above type and their preparation are described, for example, in U. Dietrich et al., J. Am. Chem. Soc. 1999, 121, 4348-4355.
Non-limiting examples of metallocene compounds of the formula (IV) containing a moiety of formula (VI) are:
dimethylsilandiyl-4-(3-methyl-1-phenylcyclopentadienyl-[2,1-b]-pyrrol)-9-(xcex75-fluorenyl)-zirconium dichloride and dimethyl;
dimethylsilandiyl-4-(3-ethyl-1-phenylcyclopentadienyl-[2,1-b]-pyrrol)-9-(xcex75-fluorenyl)-zirconium dichloride and dimethyl;
dimethylsilandiyl-4-(3-isopropyl-1-phenylcyclopentadienyl-[2,1-b]-pyrrol)-9-(xcex75-fluorenyl)-zirconium dichloride and dimethyl;
dimethylsilandiyl-6-(2,5-dimethyl-3-phenylcyclopentadienyl-[1,2-b]-thiophene)zirconium dichloride and dimethyl.
Metallocene compounds of formula (I) and (IV) and their methods of preparation are described in the copending Application PCT/EP00/13191 in the name of the same Applicant.
The first stage of the polymerization (A) can be carried out in liquid phase, or in gas phase, working in one or more reactors. The liquid phase is generally an inert hydrocarbon, such as hexane or toluene, or can be one or more olefins, i.e. a liquid monomer process. The gas-phase polymerization can be carried out in one or more fluidised bed reactors or wherein the bed is agitated mechanically.
The treatment stage (II) can be carried out by contacting the polymer obtained under stage (I) with a solution of the metallocene in a hydrocarbon solvent, such as hexane or toluene optionally in the presence of a suitable cocatalyst and/or an Al-alkyl compound. Preferably said solution contains a suitable cocatalyst, such as an alumoxane, or a compound able to form an alkylmetallocene cation and an Al-alkyl compound used as scavenger.
Examples of alumoxanes suitable for use according to the present invention are methylalumoxane (MAO), isobutylalumoxane (TIBAO) and 2,4,4-trimethyl-pentylalumoxane (TIOAO). The molar ratio between the aluminium and the metal of the metallocene compound is in general comprised from 10:1 to 20000:1, preferably from 100:1 to 5000:1, more preferably from 10:1 to 5000:1, even more preferably from 100:1 to 1000:1.
Non-limiting examples of compounds able to form an alkylmetallocene cation are compounds of the formula D+Exe2x88x92, wherein D+ is a Broensted acid, able to donate a proton and to react irreversibly with a substituent X of the compound of the formula (I), and Exe2x88x92 is a compatible anion which does not coordinate and which is able to stabilise the active catalytic species which results from the reaction of the two compounds and which is sufficiently labile to be displaceable by an olefin substrate. Preferably, the anion Exe2x88x92 consists of one or more boron atoms. More preferably, the anion Exe2x88x92 is an anion of the formula BAr4(xe2x88x92), wherein the substituents Ar which can be identical or different are aryl radicals such as phenyl, pentafluorophenyl or bis(trifluoromethyl)phenyl. Tetrakis-pentafluorophenyl borate is particularly preferred. Moreover, compounds of the formula BAr3 can conveniently be used. Compounds of this type are described, for example, in the published International patent application WO 92/00333. Further, compounds of the formula R27Mxe2x80x94Oxe2x80x94MR27, R27 being an alkyl or aryl group, and M is selected from an element of the Group 13 of the Periodic Table of the Elements (IUPAC). Compounds of this type are described, for example, in the International patent application WO 99/40129. Examples of Al-alkyl compounds are trimethylaluninum (TMA), tris(2,4,4-trimethyl-pentyl)aluminum (TIOA), tris(2-methyl-propyl)aluminum (TIBA), tris(2,3,3-trimethyl-butyl)aluminum, tris(2,3-dimethyl-hexyl)aluminum, tris(2,3-dimethyl-butyl)aluminum, tris(2,3-dimethyl-pentyl)aluminum, tris(2,3-dimethyl-heptyl)aluminum, tris(2-methyl-3-ethyl-pentyl)aluminum and tris(2-ethyl-3,3-dimethyl-butyl).
The treatment stage (II) can be carried out by suspending the polymer obtained in (I) in a hydrocarbon solvent, which contains the metallocene compound of formula (I) and optionally the cocatalyst. The working temperature generally ranges from 0 to 100xc2x0 C., preferably 10 to 60xc2x0 C. The solvent can be removed at the end of the treatment. It is also possible to contact the polymer produced under (I) with a solution of the metallocene compound containing a minimum of solvent. When the treatment stage (II) is carried out in a gas phase a loop reactor can be used, wherein the polymer obtained under step (I) is circulated by a stream of inert gas. The loop reactor is fed, for example with a sprayer, with a solution of the metallocene compound optionally containing the cocatalyst, in order to obtain a free-flowing product.
The quantity of the metallocene contained in the product obtained from the treatment stage (II) can vary over a wide range depending on the metallocene used and on the relative amount of product desired in the various stages. Generally, said quantity is from 1xc3x9710xe2x88x927 to 1xc3x9710xe2x88x923 g of the metallocene/g of product, preferably from 5xc3x9710xe2x88x927 to 5xc3x9710xe2x88x924, more preferably from 1xc3x9710xe2x88x926 to 1xc3x9710xe2x88x924.
The deactivation, if any, of the catalyst used in (I) prior to the contact treatment with the metallocene is carried out with a compound that is capable of deactivating the catalyst present in the product obtained in step (I). Preferably the compound capable of deactivating the catalyst is selected from the group consisting of CO, COS, CS2, CO2, O2, acetylenic compounds, allenic compounds and compounds of general formula R28y-1X3H in which R28 is hydrogen or a hydrocarbon group with from 1 to 10 carbon atoms, X3 is oxygen, nitrogen or sulphur and y is the valence of X.
Non-limiting examples of compounds for use as a deactivating agent can be found in U.S. Pat. No. 5,648,422, the disclosure of which being incorporated herein by reference.
The polymerization step (III) can be carried out in liquid phase, gas phase or suspension. The liquid phase can be carried out in an inert hydrocarbon solvent or in one or more olefins, i.e liquid monomer process. The gas-phase process can be carried out in a reactor equipped with a fluidised bed or a mechanically stirred bed. During the second polymerization of step (III) it is convenient to feed into the polymerization reactor an Al-alkyl compound as described above and an alumoxane compound, such as methylalumixane. Generally the Al-alkyl compound is fed into the reactor during the polymerization step (III) when the treatment step (II) has been carried out without an Al-alkyl compound.
The amount of polymer produced in stage (I) is generally higher than 2000 g/g of solid component, preferably higher than 3000 g/g of solid component, and more preferably higher than 5000 g/g of solid component.
The catalyst used in the first stage (I) comprises the product obtainable by contact treatment of:
(a) a solid component comprising a compound of a transition metal M selected from Ti or V and not containing a M-xcfx80 bond, supported on magnesium halide. The solid component can also comprise an electron-donor compound, i.e. an internal donor. Generally, internal donors are used when the solid component is used for the preparation of catalysts for the stereospecific polymerization of alpha-olefins, such as propylene, in order to obtain highly stereospecific polymers having an isotacticity value of higher than 90;
(b) an Al-alkyl compound and optionally an electron donor compound, i.e. an external donor.
The halides of magnesium, preferably MgCl2, in active form, used as support for Ziegler-Natta catalysts are well know and described in, for example, U.S. Pat. Nos. 4,298,718 and 4,495,338.
The compound of the non-metallocene compound is selected from the group consisting of Ti-halides, Ti-halo-alkoxides, VCl3, VCl4, VOCl3 and halo alkoxides of V.
When titanium compounds are used, the preferred are TiCl4, TiCl3, and the halo alkoxides of the formula Ti(OR29)kXl, wherein R29 is a hydrogen radical with 1-12 carbon atoms or a xe2x80x94COR1 group, X is a halogen and (k+1) is the valence of titanium.
Internal donors are selected from ethers, esters, amines, ketones. Particular useful internal donors are 1,3-diethers, which are described, for instance, in EP-A-361493.
The Al-alkyl compound is generally selected from a trialkylaluminium compound. Non-limiting examples of aluminium compounds are Al(Me)3, Al(Et)3, AlH(Et)2, Al(iBu)3, AlH(iBu)2, Al(iHex)3, Al(iOct)3, AlH(iOct)2, Al(C6H5)3, Al(CH2xe2x80x94CH(Me)CH(Me)2)3, Al(CH2C6H5)3, Al(CH2CMe3)3, Al(CH2SiMe3)3, Al(Me)2iBu, Al(Me)2Et, AlMe(Et)2, AlMe(iBu)2, Al(Me)2iBu, Al(Me)2Cl, Al(Et)2Cl, AlEtCl2 and Al2(Et)3Cl3, wherein Me=methyl, Et=ethyl, iBu=isobutyl, iHex=isohexyl, iOct=2,4,4-trimethyl-pentyl. The above mentioned Al-alkyl compounds can be used either alone or in mixtures thereof.
Amongst the above aluminium compounds, trimethylaluminium (TMA), triisobutylaluminium (TIBAL) and tris(2,4,4-trimethyl-pentyl)aluminium (TIOA) are preferred.
The external donor can be the same as the internal donor, or can be different therefrom. External donors are generally selected from silicon compounds of formula R30R31Si(OR32)2, wherein R30, R31 and R32 are a C1-C20-alkyl or a C6-Cl12-aryl group. Non limiting examples are methylcyclohexyldimethoxysilane and diphenyldimethoxysilane.
The polymer produced in step (I) is an essentially isotactic propylene polymer as defined under component (B) of the composition of the present invention.
The polymer produced in step (III) is a flexible propylene polymer having reduced isotacticity as defined under component (A) of the composition of the present invention.
The compositions according to the present invention can be used as a flexible material and as a compatibilizer for blends of amorphous and crystalline polyolefins.
The thermoplastic compositions of the present invention can also be prepared by mixing the components in generally known mixers, such as a Banbury mixer.
The compositions of the present invention are generally obtained in the form of pellets. These pellets can be converted into articles by generally known processing methods of thermoplastic materials, such as moulding, extrusion, injection and the like. It is a further aspect of the present invention to provide manufactured articles obtainable from a thermoplastic composition of the present invention.
In particular, the manufactured articles according to the present invention obtained by moulding processes are endowed with flexible properties, which are of particular interest for articles for which high deformation and elongation is required.
Films obtained by the thermoplastic compositions of the present invention by extrusion processes are particularly useful in the field of low-temperature-heat-sealing films.
The data of the following examples indicate that the compositions of the present invention, differently from the individual components, have elasto-mechanical properties, which make them particularly useful for the preparation of articles for which high flexibility is required.
The component (A) generally has very high flexibility as it is shown by very low flexural modulus, low strength at yield and high elongation at yield. The component (B) shows very high flexural modulus, high strength at yield and low elongation at yield. These characteristics reflect a much stiffer material, which is unsatisfactory when high flexibility is required.
When an application requires a certain set of flexible-mechanical properties within the limits of the component (A) and (B), it is achievable by modulation of the composition of the present invention. Further, the compositions of the present invention are endowed with good transparency. The compositions of the present invention have a sealing-initiation-temperature (SIT), which is substantially lower than the films obtained from (B) alone.
In particular the composition of the present invention have the following characteristics:
Melt Flow Rate (METHOD ASTM D1238) comprised from 5 to 200
Elongation at break (METHOD ASTM D 412)  greater than 600%, preferably  greater than 800%;
Flexural modulus (Exe2x80x2) (METHOD ASTM D-5023) comprised from 100 Mpa to 1200 Mpa; preferably from 100 to 800;
HAZE (on 1 mm compression moulded plaque METHOD ASTM D1003) comprised from 20% to 50%;
GLOSS (60xc2x0) (on 1 mm compression moulded plaque METHOD ASTM 2457) comprised from 50% to 90% and
Sealing Initiation Temperature (measured according to the procedure reported in the examples) comprised from 80xc2x0 C. to 130xc2x0 C.
The composition of the present invention can be used together with a further polymeric material, such as a crystalline, semicrystalline or rubber like material, in order to obtain a ternary composition.
The present invention is illustrated by means of the following examples, which are given solely for illustrative purposes and are not intended to limit the scope of the invention.